Apparatus for stretching elastic covers



V. H. HASSELQUIST APPARATUS FOR STRETCHING ELASTIC COVERS Feb. 22, 1949.

5 $heets-Sheet 1 Filed Jan. 24, 1944 .Y L/ eiba. 227 .5155

v. H. HASSELQUIST 2,462,318

APPARATUS FOR STRETGHING ELASTIC COVERS Feb. 22, 1949.

3 Sheets-Sheet 2 Filed Jan. 24, 1944 JUL/5775b M27272 Feb. 22, 1949. v. H. HASSELQUIST APPARATUS FOR STRETCHING ELASTIC COVERS 3 Sheets-Sheet 5 Filed Jan. 24, 1944 Patented Feb. 22, 1949 UNITED STATES OFFICE APPARATUS FOR STRETCHING ELASTIC COVERS 14 Claims.

This invention relates to apparatus for stretching elastic covers about surfaces of aircraft and is especially useful for applying ice-removing .covers to the surface of airfoils.

Elastic ice-removing covers have been secured :about the leading edges of wings and other airfoils by rows of hollow tubular rivets secured to :the skin of the airfoil and having threaded bores 1, for receiving screws. The covers have been provided with rows of apertures along their margins :for passage of the screws, and fairing strips of 1metal, also'having apertures for receiving the retaining screws sometimes have been applied over :the' margins of the covers.

Stretching of the covers to secure them in place under tension has been difficult to accomplish by hand, especially where the covers are of large size. Efforts to stretch the covers by pulling their ;margins from positions at the rear of the line --of attaching rivets have involved difficulties because of the presence of the airfoil surface, and --these difficulties have been aggravated with wings of large size.

The principal objects of the present invention :are to provide tensioning of the elastic cover by j pushing movement, which makes possible operation in the free space in front of the leading edge of the airfoil, to provide for pushing one ofthe :z'nargins to position by a leverage system secured 2 to the attaching screws of the opposite margin and fulcrumed thereabout, to provide for simulitaneously stretching a broad span of the cover, :and to provide for convenience and for economy of eiiort and simplicity of handling.

These and other objects will appear from the "following description and the accompanying drawings.

Of the drawings,

Fig, 1 is a plan view of apparatus constructed "in accordance with and embodying the invention, showing the apparatus in use in association with .an airfoil and elastic cover, parts being broken away. 7

Fig. 2 is a sectional elevation thereof, taken on line 22 of Fig. 1, the position of the cover before stretching being indicated in dot and dash lines.

Fig. 3 is a detail view in perspective of an anchoring hook.

Fig. lis a detail sectional view taken on line 4-4 of Fig. 2, parts being broken away.

Fig. 5 is a side elevation of a modification of theinvention, the airfoil being shown in section, the initial position of the apparatus being shown in dot and dash lines.

Figs. '6, 'l and 8 are side elevations showing further modifications of the invention, the airfoil being shown in section.

Q is a detail sectional view thereof taken on line 3+9 of Fig. 8.

Fig. iOis a side elevation of another modification of the invention, the airfoil being shown in section. v

Fig, 11 is a detail perspective view of the clamp thereof. I v

Fig, 12 is a side elevation of another modification of the invention, the airfoil being shown it section.

Referring to the drawings, and first to Figs. 1 to '4' thereof, the numeral iii designates anelastic ice-removing c'c'veringin the process of being applied chordwise about the nose of anairfoil H in a' 'conditi0n of chordw'ise tension. The covering is at least partially of rubber or other rubbers like material may have inflatable pockets ['2 formed therein for distorting the covering to remove fee formed thereon. v For securing the coveri'ng to the airfoil, the latter is provided with hollow internally threaded rivets 24 arranged in a row along itsupper surface for receiving retaining screws l5, and similar rivets it are aranged in row along itslower surface for receiving similar retaining screws, to engage apertures in the margins of the covering. The'cove'ring may be reinforced at itsmargin by stiffening beads ll, [8 of metal to distribute the load between the screws. For providing a smooth contour at the ma'rginsof the covering, metal fairing strips 20', 2-! are provided, and these have countersunk openings to receive the screw heads. One margin of each fairin strip rests upon a margin of the covering when in place, and the othermargin thereof rests upon the surface of the airfoil. 7

In attaching the covering, assuming that the airfoil is in a horizontal position and that the rivets i4 and it are in place, the covering is preferably first secured to the rivets I l at the upper surface of the airfoil, and then stretched about the noseof the airfoil until its lower margin can be secured to the rivets it. This requires considerable force, especially where the coverings are of great horizontal extent, whether the whole margin be stretched at once or the stretching be accomplished by stretching and applying the lower margin progressively.

For stretching the covering in place, a flexible tension men'ib r 25, such as a chain, is attached at one" end thereof to one or more of the screws l5 which are left partially protruding for this purpose. The other end of the tension member -one end which engages over the bar 28.

is secured to one end of a strut member 28. The opposite end of the strut member is adapted to engage a bifurcated hook 2! attached to the lower margin of the covering ID with its hooked limbs engaging the upper and lower ends of a screw passed through an aperture of the covering. By exerting pressure downwardly against the strut member where it engages the tension member, a pushing force is exerted against the lower margin of the covering efiecting a stretching of the covering about the nose of the airfoil.

In practicing the invention a plurality of strut members 26 and tension members 25 may be employed in unison to simultaneously stretch a wide reach of the covering or an entire covering in a single operation. For this purpose a series of hooks 21 may loosely support a bar 28, as shown in Fig. 4. Each hook is engaged about a screw 29 inserted through an aperture in the lower margin of the covering. Each strut 26 has a hook 30 on For anchoring the tension members 25 to the screws l5, hooks 3| (see Fig. 3) are provided, each having thin hooked ends 32, 33 for engaging about a pair of screws l above the covering. A plurality of hooks 3| may be engaged by an equalizer 34 which in turn is secured to a tension member 25. Any number of strut members 28 may be hooked over the bar 28 to push the lower margin of the covering into place.

For adjusting the relative disposition of the tension members and strut members, the struts, which are preferably of tubular form, may have longitudinal slots 35 at their outer ends, and of such width that they engage snugly between links of chains employed as the tension members but prevent the chain sliding therethrough. In starting the stretching operation, the hooks 21 are attached to the lower margin of the covering, which hangs free as shown in dot and dash lines in Fig. 2, the strut members 25 are hooked over the bar 28 engaged by the books 21, and the tension members 25 are attached to the strut members at the desired position. The strut members may then be forced downwardly by pressure applied at the portion thereof where they engage the chain tension members to stretch the covering.

For applying a constant pressure, an eyebolt 36 may be provided at the outer end of a strut member, and weights 3'! may be secured to the eyebolt. With this arrangement, weights may be applied until the covering is stretched to a position where the screws in its lower margin are in alignment with rivets IS. The stretching apparatus is then kept in place while an operator enters the screws in the rivets and turns them partly into place. It is found that in the stretched position the apparatus is nicely balanced and may be shifted easily by hand to bring the screws into exact alignment with the rivets.

After the screws are started, the stretching apparatus is removed and the screws driven in place.

Where the airfoil is in horizontal position and it is desired to apply the lower margin of the covering first, the stretching apparatus of Fig. 5 is desirable. Referring to this figure of the drawing, the strut member 48 has a hooked end 4| for engaging over a bar 42 which engages hooks 43 similar in construction to the hooks 21 of Fig. 4. At the opposite end of the strut, the strut is formed with a yoke 44. A shackle 45 is pivotally mounted on the yoke and a tension member 46 has one end secured to the shackle and the other end to an anchoring hook 41, similar to the hook shown in Fig. 3.

With the hook 41 anchored to screws 48 by which the lower margin of the covering 48 is secured to the airfoil, and the strut 48 engaging the bar 42, a force exerted upwardly against the strut at the yoke end thereof stretches the covering 48 by pushing its upper margin about the upper surface of the airfoil while the tension member 46 fulcrums about the hook 4'! providing the reaction force.

For holding the apparatus at its position of final adjustment to permit the operator to secure the screws 58 in place, a standard 5| is provided having a base 52 resting on the floor. A clamp collar 53 is slideably mounted on the standard but may be locked thereto at any desired position by a clamp screw 54. The collar 53 extends through the yoke 44 which bears thereon, a shoulder being provided thereon for supporting it. The arrangement is such that with the screw 54 loosened the collar 53 with the strut member may be lifted with respect to the standard to push the upper margin of the covering into its position of attachment and the collar may then be secured to the standard to free the workman for securing screws 58 in place.

In the form of the invention of Fig. 6, the strut member 50 has a hooked end SI for engaging over a bar 62 which in turn engages the hooks 58 which engage the screws 64 passed through the lower unsecured margin of the covering 65. The upper margin of the covering is secured to the airfoil 85 by screws 61. Hooks 68, similar to the hooks of Fig. 3, are secured about the screws 5'1. The strut member 60 has a vertical arm 68 integral therewith. A tension member 68a has one end secured to the hooks 68 and the other end secured to the arm 68. Pressure applied downwardly on the outer end of the strut member 88 causes the apparatus to fulcrum about the hooks 63 and the lower margin of the covering is pushed into final position by stretching of the covering. The retaining screws 64 are then entered in the rivets 69 and the stretching apparatus is removed. Whereupon the screws 61 and 64 are driven home.

In the form of the invention shown in Fig. '7, the covering 10 is shown as attached along its lower margin to an airfoil H by screws 12 engaging hollow rivets 13. The upper margin of the covering is to be secured to hollow rivets 14 by similar screws engaging apertures 15 in the margin. For stretching the covering a stiff tension member 16 has a claw ll fixed to one end thereof for engaging under the head of one of the screws 12. It has a clamp collar 18 at its opposite end adapted to engage over a bar 19 and to be clamped thereto at any position therealong by a hand screw 80. Mounted on the bar is a second clamp collar 8| adapted to be clamped thereto by a hand screw 82. The collar 8! is also provided with a radially-extending arm 85 and an ear 86 adjacent thereto. A strut member 81 is hinged to the ear 85. A tension screw 88 is hinged to the arm 85 and has a wing nut 88 threaded thereon. A compression coil spring surrounds the tension screw between the wing nut and the strut 81.

Hingedly mounted on the end of the strut 81, as at 94 is a shoe 9| adapted to frictionally engage the outer surface of the covering 10. The shoe has a pad 92 of friction material, such as rubber on its face. A lever 83 is fixed to the strut 81 near the friction shoe. The arrangement is such that the collar 8| and the wing nut 89 may be adjusted to engage the surface of the covering near its upper margin with some p3:es a r-e and-the lever 93 may then be forced to the -l ett in Fig. '7 to cause the apparatus to rotateabout the claw 12 as -a center-in a-countercloekwisedirection with the pad 92 engaging the covering and pushing it about the airfoil 1! in the-direction of the rivets 14, thereby stretching the covering to a position where the screws may be entered in the hollow rivets 14 through the apertures 15.-

The. apparatus shown-in Fig, 8 is adapted to push both margins of the covering Idointo place about the nose of the airfoil I4] simultaneously toalign; its screw' apertures with the threaded hollow rivets I42, I43 secured to the skin of the airfoil. For this purpose, a pair of parallel tubular tension members 144, I 35 have claw hooks I46, I41 secured -to ends thereof adapted to engage screws inserted in the rivets I42, I43. Within-thetension members are strut members I48; I49; The strut members each has a laterally pro jecting finger I56 which extends through a;.1ongitudinal slot II formed in the wall of the tubular tension member and is adapted to engage in an aperture in the margin of the covering. Each strut member is also formed with a rack I52 for propelling it along the tension member in which it is adapted to slide.

At a positionalong each tension member, a housing I 55is fixed to the member and has bearings. l56-for rotatably supporting a shaft I51 which extendsthrough both housings. A gear I58 -i s slideably mounted on the shaft I51 which has a keyway I59 for engaging a feather key fixed to the gear. The gear extends through a slot; inthe tension member and meshes with the rack-of the strut member. A crank I66 is fixed tothe shaft I51 for rotating it. The arrangementis such that by rotating the shaft E51 the strut members may-be advanced along the tension-members to push the margins of the cover- 1 ing-toward the hooks I46, I41 and thereby stretch the covering into place. For holding the tension members in properly spaced apart relation, collars I65, I66 are provided at each side of each housing and have set screws for securing them to theshaftin any position of adjustment. For

lockingthe racks in any position of adjustment,

a; pawl IGI is pivoted on the housing I55.

In the use of this form of the invention, the

apparatus; is; adjusted sothat the claws I46, I41

engage screws inserted in the rivets I42, I43. The fingers I50 are inserted in screw holes in the opposite -margins of the covering. The crank I60 is then operated to advance the strut members and the margins of the covering to a position where the screw holes align with the screws. Screws may then be inserted in adjacent screw hqlestothoseengaged by the fingers I56 to hold the covering in place.

Referring to Figs. and 11, the covering H6 is shown as secured at its upper margin to the airfoil III by screws engaging in the hollow rivets II2. A hook member II3, similar to that shown in Fig. 3 is hooked under the fairing strip II4 about screws entered in the hollow rivets I I2. The lower margin of the covering is gripped by a clamp member I61 (see Fig. 11) having a hook I68. For pushing the lower margin of the covering into place a tension member H5 is provided with a claw II5a for engaging a screw entered in a hollow rivet I I1. The tension member II5 has a pair of threaded ears H8, H9 through which a threaded thrust member I extends. A crank I2I is fixed to the thrust member. A swivel pressure plate I22 is mounted on the end 0ivthepthrustmemberiandis formed with: a hook forengaging overra-bar' I23: Theabar: I23 is adapted to engage-simultaneously:a plus rality of the clamping membersbytheir'hook: portions I68. Each, clamp member hasahstae tionary jaw- I24 and a movable. springrjaw: I257. adapted'to be pressed toward the stationaryz'jaw" by a cam I26; actuated. by a leverI21'..

For supporting the; apparatus; auflexiblerten sion member IE8 .is attachedto the hook-:mema ber H3 and has its lower end secured to. thesearr II9. The-arrangementis suchth'at' when the crank I2I is.rotated-inonedirection; the bar: I23 is forced to the left irrFig. 10 against the hooks I68 forcing thelowermargin ofzthewcov ering into place where the screwsmay beentered in the tubular rivets .I I1:

In the form :of the invention shown in Fig. 12,? one margin of the covering I16 has been: secured by screws entering hollow-rivets I1I secured to an airfoil I12 which is located in a position'wit-h its nose downwardly; For pushing the other margin, into a position where perforations :for screwsv in the margin are over hollow rivets I13," a; bar-I14 having a series of hooks I15, similar tothe'hooks- 21 shown in Fig. 4, is-secured by means of tliehooks engaging screws inserted in the-perfora tions of the margin of thecovering.

A jack I16, preferably-of thetype in which a moveable step I11 is adapted to:be adjustedalong a strut member I18 by operation of a handle I19;-v has a ball-joint I86 connecting it to. anon-slip ping floorr'plate I81- The floor plate has 'a suction: rubber shoe I82 for engaging the .fioor.-.I83.at any: position. The arrangement is. such .that the: moveable step. I11 may be engaged under'the bar I16 and adjusted up the strut member -I.18:topush the margin into. placesothat the-screws can be entered. in the hollow rivets I13.

Due to the'moveable floor plate andi the-balls; connection, the strut I18.may be adjusted toanydesired angular relation to the floor; This. has the advantage of providing for lateral adjustment as well as vertical adjustment. of .the margin on: the cover to align the screw holes accurately with the hollow rivets.

Variations may bev made withoutgdeparting from the scope of the invention as it is definedby': the following. claims.

I claim:

1; Apparatus for stretching an-elastic coveringabout a curved surface while a margin-ofthecovering is restrained against yielding by securing means engaging said-surfacesaid apparatus com: prising means for holding; the opposite'marg-in: of the coveringend means including a-tension element having attachment to said securing means for pushing said holding means in-a direction to stretch the covering-said pushing means including. j

said tensionelement being fulcrumed at 'said securing means for movement as a unit'about' said securing means.

2. Apparatus for stretching an elastic covering to a curved surface While a margin of the covering is restrained against yielding by securing means engaging said surface, said apparatus comprising means for holding the opposite margin of the covering, means including a tension element having attachment to said securing means for pushing said holding means in a direction to stretch the covering, and means for supporting the pushing means including said tension means for movement as a unit about said securing means.

3. Apparatus for stretching an elastic covering amasie' about a curved surface while a margin of the covering is restrained against yielding, said apparatus comprising means for holding the opposite margin of the covering, and means for positioning said opposite margin in place, said lastnamed means comprising a strut member engaging said opposite margin, a tension member connecting said strut member to an element on the surface, and means for shifting the positions of said strut and tension means to stretch the covering.

4. Apparatus for applying an elastic covering to a curved surface, said apparatus comprising tension means including means for engaging a projection on the surface and a flexible member extending therefrom, and strut means for engaging at one end thereof a margin of the covering and at the opposite end a free portion of said flexible member.

5. Apparatus for applying an elastic covering to a curved surface, said apparatus comprising tension means including means for engaging a projection on the surface and a flexible member extending therefrom, strut means associated with said tension means, and means for moving said tension and strut means in a direction to stretch the covering.

6. Apparatus for applying an elastic covering to a curved surface, said apparatus comprising tension means including means for engaging a projection on the surface and a flexible member extending therefrom, strut means associated with said tension means, means for adjusting said strut and tension means as a unit in a direction to stretch the covering, and means in addition to said tension means for holding said strut and tension means in a position of adjustment.

7. Apparatus for stretching an elastic covering about the leading edge of an airfoil while a margin of said covering is retained by elements in the surface of the airfoil, said apparatus comprising means for engaging said covering at a position spaced from said elements chordwise, and means for pushing the engaging means to stretch the covering.

8. Apparatus as defined in claim 7 in which the covering-engaging means comprises a friction pad.

9. Apparatus as defined in claim '7 in which the covering-engaging means comprises hooks for engaging projecting elements in the margin of said covering.

10. Apparatus for stretching an elastic covering about the leading edge of an airfoil While a margin of said covering is retained by elements in the surface of the airfoil, said apparatus comprising means for engaging said covering at a position spaced from said elements chordwise, and means for pushing the engaging means to stretch the covering, the last said means including reaction means for engaging said elements.

11. Apparatus for stretching an elastic covering about the leading edge of a curved surface such as an airfoil while a margin of the covering is restrained at one side of said leading edge against yielding, said apparatus comprising means for holding the opposite margin of the covering, and strut means connected to said holding means including means engageable with a. projection on said surface at the other side of the leading edge and operable from in front of said projection to direct said opposite margin of the covering to said projection.

12. Apparatus for stretching an elastic covering about the leading edge of a curved surface such as an airfoil While a margin of the covering is restrained at one side of said leading edge against yilelding, said apparatus comprising means for holding the opposite margin of the covering, a member engageable with a projection on said surface at the other side of the leading edge, and strut means connected to said holding means and having a pivotal mounting with said member for swinging movement from in front of said projection to direct said opposite margin of the covering to said projection.

13. Apparatus for stretching an elastic covering about a curved surface while a margin of the covering is restrained against yielding by securing means at said margin engaging said surface, said apparatus comprising means for engaging the opposite margin of the covering, and swinging means including a tension element having at one end thereof attachment to said surface at said securing means, and strut means having one end engaging said tension element at a position remote from said securing means and the opposite end engaging the free margin of the covering, said swinging means being fulcrumed at said securing means for movement as a unit thereabout.

14. Apparatus for stretching an elastic cover ing about the leading edge of an airfoil, said apparatus comprising elements connected to each other for engaging said covering at positions spaced-apart chordwise, and means for moving an element with respect to the other for stretching said covering upon said surface, said means comprising a strut element extending forwardly of the airfoil for manipulation in advance of said leading edge.

VICTOR H. HASSELQUIST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 848,300 Foltz Mar. 26, 1907 

